This invention related to a fuel delivery control apparatus for controlling the amount of fuel metered to an internal combustion engine and, more particularly, to an apparatus for learning an acceleration enrichment related correction factor used in correcting the amount of fuel metered to the engine to provide acceleration enrichment in response to a demand for engine acceleration.
For example, Japanese Patent Kokai No. 63-41634 discloses a fuel delivery control apparatus for controlling the amount of fuel metered to an internal combustion engine. The fuel delivery control apparatus employs a digital computer for calculating a desired value for fuel delivery requirement in the form of fuel-injection pulse-width and timing. A basic fuel-injection pulse-width value Tp is calculated by the digital computer central processing unit as Tp=K.times.Q/N where K is a constant, Q is the intake air flow and N is the engine speed. The calculated basic value Tp is then corrected for various engine operating parameters. The corrected fuel-injection pulse-width value Ti is given as EQU Ti=Tp.times.COEF.times.ALPHA+Ts
where ALPHA is a correction factor related to the oxygen content of the exhaust gases for providing a closed loop air/fuel ratio control, Ts is a correction factor related to the voltage of the car battery, and COEF is a correction factor given as EQU COEF=1+KTw+KMR+KAS+KAI+KFUEL+
where KTw is a correction factor decreasing as the engine coolant temperature increases, KMR is a correction factor related to a desired air/fuel ratio, KAS is a correction factor for providing fuel enrichment control when the engine is cranking, KAI is a correction factor for providing fuel enrichment control when the engine is idling, and KFUEL is a correction factor for providing fuel enrichment control when the engine is accelerating. The calculated values for fuel-injection pulse width and fuel-injection timing are transferred to a fuel-injection-control logic circuit. The fuel-injection-control logic circuit then sets the fuel-injection timing and fuel-injection pulse-width according to the calculated values for them.
The correction factor KFUEL is found from a predetermined relationship stored in the read only memory of the digital computer. The predetermined relationship defines correction factor KFUEL as a function of engine operating conditions. Since the relationship cannot be modified after it is stored in the read only memory, however, the correction factor KFUEL will deviate from an optimum value, causing degraded drivability and harmful emission increase due to engine and fuel delivery system changes with time.